Abstract
Recurrent selection is being used to improve Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4) resistance in Upland (Gossypium hirsutum L.) and Pima (G. barbadense L.) cotton using naturally infested fields and artificially inoculum-greenhouse sites. Our primary objective is to introduce a known FOV4 dominant gene that has shown resistance in Pima into the Upland species. In 2013, 2014 and 2015, we evaluated 1155 entries for resistance. These entries were exposed to FOV4 pressure in naturally infested fields and rated. Selected entries were then self- and cross pollinated. Parental lines and F1 populations were then inoculated with FOV4 and grown under greenhouse conditions for rating and reselection. This research will provide additional germplasm to broaden the genetic base for FOV4 resistant cotton.
Introduction
In California, Fusarium wilt of cotton is a serious fungal disease that is caused by Fusarium oxysporum f. sp. vasinfectum (FOV). Practices that have reduced the effects include not planting in sandy or sandy-loam textured soils that have a high infestation of root knot nematode and use crop rotation to help manage soil inoculum levels. This has been useful with FOV races 1 and 3, but Fusarium oxysporum f. sp. vasinfectum (FOV4) has been found to cause substantial damage in the absence of root knot nematode (Meloidogyne incognita) and persists even when crop rotation is practiced. Thus, the only long-term management of FOV4 is developing resistant cultivars. One objective of this study is to evaluate a known resistant FOV4 dominant gene from Pima (PS6) for potential introgression into Upland germplasm. The second objective is to identify and develop Upland germplasm…
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Update FOV4 research progress update USDA-ARS and Univ. of California
PIs Drs. Mauricio Ulloa and Robert B. Hutmacher
Fusarium wilt race 4 [Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4)] research progress update – cooperative efforts by the USDA-ARS, PA, CSRL, Plant Stress and Germplasm Development Research (PSGD), Lubbock, TX, the University of California Cooperative Extension UC-ANR, and the University of CA Davis Plant Sciences Dept.
In all today, 1,155 entries have been evaluated in infested FOV4 fields and a portion (1/4) in the greenhouse using artificial FOV4 inoculation. Our primary objectives are to introduce a known FOV4 dominant gene that has shown resistance in Pima (e.g., Pima-S6) into Upland cultivars, and identify/develop within the Upland gene pool improved FOV4 tolerant germplasm. Entries have been planted in naturally-infested FOV4 fields and seeded in 5 x 1 meter plots and replicated three times. During the growing season, plant responses to inoculum pressure were assessed through evaluations of root and stem vascular staining levels, plant mortality, foliar wilt symptoms and measures of relative plant vigor. Selected cotton entries used as parents to make crosses and progeny developed from these parental entries (F1 populations) were also inoculated with FOV4 and grown under greenhouse conditions for rating and reselection. In 2013, we evaluated 511 entries in the field, including progeny from the “PS6 X TM1” and “TM1 X PS6”. In 2014, we evaluated 316 new accessions and selected 39 (12%) entries for increase and introgression of Pima resistant and Upland cultivars under FOV4 field and greenhouse evaluations. In 2015, we evaluated 207 new accessions from the USDA-ARS collection that were increased in Lubbock Texas. From 207, we selected 37 (17.5%) lines. We also received 40 U.C. Riverside lines and selected only 4 (10%).
One of the breeding methodologies applied during the identification and development of these new improved FOV4 resistant cotton germplasm is “Recurrent Selection”. So far, we made 141 selections (13% of total entries), 18 recurrent selections (2% of 2013-14 entries) and made 142 crosses (F1 populations). The 54 selections…
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